1. Field of the Invention
The present invention relates to a disaster prevention system, in particular, a disaster prevention system using a LAN for connecting a plurality of fire receivers to one another or connecting a main fire receiver to a plurality of repeaters for distributed processing which can be independently monitor-controlled, so as to allow the LAN to be expanded in a free form.
2. Description of the Related Art
An example of a conventional disaster prevention system includes a distributed LAN system in which a main fire receiver and a plurality of repeaters for distributed processing which can be independently monitor-controlled are connected to one another via a LAN (for example, refer to JP 05-217088 A (page 1, FIG. 1)).
Another example of a conventional disaster prevention system includes a receiver LAN system in which a plurality of fire receivers are connected to one another via a LAN (for example, refer to JP 2002-170177 A (page 1, FIG. 1)).
In the above-mentioned conventional system such as the distributed LAN system or the receiver LAN system, the LAN as a transmission path is formed into a loop and further, for example, into a double loop in consideration of backup.
However, the conventional distributed LAN system or receiver LAN system, which includes the LAN originally formed into a loop, has a problem in that it is extremely troublesome to additionally installing a terminal device thereto because it requires the path formed into the loop to be reconfigured and rewired.
The present invention has been made to solve the problem, and has an object to provide a disaster prevention system in which the path of the LAN can be formed with flexibility so as to be expanded into a free form.
Also, a fire receiver of so-called R-type is adopted as the fire receiver used in the above-mentioned conventional distributed LAN system or receiver LAN system, which monitors and controls connected devices such as fire detectors based on transmission signals. In order to correspond to the fire receiver of R-type, the repeater for distributed processing performs monitor-control over the connected devices based on an R-type system.
In adopting the above-mentioned LAN system in the field, it is only necessary, in the case of new construction, to install from the beginning of the construction the fire receivers and the repeaters for distributed processing all of which correspond to the R-system.
However, in the case of integrating the LAN system which has already been installed in the existing building and a new LAN system into one, if the already-installed LAN system in the existing building has adopted a line-monitoring system, or a so-called P-type facilities, there has been a problem in that a complete renovation of the building is necessary in order to replace the existing P-type facilities with the R-type facilities.
Also, in order to use a line connected to the P-type fire receiver, two repeaters, that is, a repeater for receiving signals on the line to transmit the signals to an R-type distributed repeater and the R-type distributed repeater for connection to the LAN, are necessary, which leads to a problem of increase in cost and in work of wiring.
Further, it has been conventional to use a dedicated LAN to construct a disaster prevention system. The reason is that if general terminal devices are connected to the LAN, an amount of information of information signals on the LAN is increased, resulting in an delay of information relating to disaster prevention, or the disaster prevention system may be affected by an interruption of the LAN which is caused by a failure occurring in any of the other general terminal devices. When a dedicated LAN is used, however, there has been another problem in that it is not easy to share the information on the LAN via a network such as an intranet or the Internet.